Production of iron-oxide pigments



Jumus LAUX,

1. Pat ted Sept. 2521936 Q Q W N' r G M N ian'onn orion or 1B0moxrnn rromnnrs it I No Drawing I ioriginal application filed 1 5... 'Diirided 'andthis application and s iaem i s, 1327', Serial no; 218,354.

7 The present inyentionrelates' to processes for the productionfof iron oxide; pigments;

the .i'l vcntion relates toa V a finelyzdiyided iron hy'-= droxide is obtainedas aby-product from tijie s y more specifically, process 1n which reduction of aromatic nitro compound meansofiron; and ac dsor acid reacting salts.

' The invention also embraces me ew'pmdu tsamines heretofore I t1me,1nvolv1ng the llSQ'OflfOIl and an' amount of acil insufficient to dissolvethe sa1ne, tlie[ iron which is usedas the reducing agent gen orally changes lntoj whose composltion corresponds to a formula which lies between FegO and-Fe Og, This oxide 1s not useful as a color pigment and is.

other nitro compounds than'thosementioned Y of very inferior qualityon accountof its low coloring power. a i

As I have set forth in my co pending ap' plication for U. S; patent, SerialN'umber 106,969, filed on'May 5, 1926, iinelydiVided iron oxides or-iron hydroxides of high com mercial value are obtained, if the reduction is carried out under such conditions that the a I have found further,that ifthe salt present in thesolutioncontains-aluminium as metallic base, solutions of lower "concentration,

and even highly diluted solutions',-,likewise give good results. i i I According to the present inventionthe re duction of aromatic: nitro' compounds L with iron metal is carried I dilute aqueous solution of analuminiumisalt. A ready made solu'tlon of such a saltmay I '1 be employed,to'which a'further addition of] 4. acid may I known hydrolysis of aluminium salts leading J I to the production of suificient free acid for 'be unnecessary on account of the the reduction. The aluminium salt may, however, also be produced during the reaction, 7 i; e., 10y thea'dd-ition'to the required quantity of iron of a certain quantity of metallic al'u minium. For the purpose of this invention processes,

finely divided yellow hydroxldized iron as a c0. 3 1

In, the methods of producing aromatic known anduscd for a long I i ai-brown-black oxide hydroxy-,

reaction mixture is a and aook s.

outin the presence of a average contentoi'r Violet red' 'iron"oxide pigment.

I aluminium chloride in 310' l lian't red iron oxide pigment nor in the presence parting in other respects from thecustomary ples 'hereinafterset forth) there remains,

as willbe evidenc'ed bythe exam,

v onunit:oiN EN-on 'rHE-R INE, ennMAN?, assrerion'roilejrnnisnu- INDUSTRIE AKrIE GEsEL so ArT, onrnnmrronr-ournnmnrn;GERM NY, 1A 1 September 7, 192 6 SerialiNof lfi-gga;and infiiermany August2O};

fofa diluted aluminium f salt solutionl(the process not essentially deafter theseparationof' the aromatic amine,

for example, aniline, resulting from the nitro" ide of the trivalent'iron oxide Fe O After levigation, washing out and drying,this 'h-y-Q the .oxif droxide is useful as a"c o1or.p1gment eitherdirectly or, if being subjected" examples. 1 It is t'og be understood, however,

' that the process accordingftothepresent ill-' VGIltlZOIl 1s capable-pf being carried outwith I Q in these examples; for example, with chlor-, and amino-nitr-o' compounds, polynitro, compounds and fnitrosulfonic acids. Other aluminium salts, can heiused in place of the chloride- Besides'the aluminium salt the solutonsf may contain j other in low concentration.

d ha e are: desi ed, after to p h mary calcination. 3

The process is illustrated loythe following 76 i due to the heat'of reaction. When the'reductio'n is fins "ished the resulting aniline is separatedin' the well-known manner There remains a yellowish brown slurry, which is separated The temp'erafromftjhe excess of metalliciron and dried.

It consists jf af iron U 2%. ff f r bi is? convert d B' f, oalcination it,

hydroxideahaving an ned'wateri.-- 3 to'fa deep,

none are reduced inia solution 051 8. kgs. of,

QOOfkgs. otiron; v 'ortho-toluidin'e produced, a" yellow hydrox- 12% is"- ohtained" from product, on'heating to 500? soluble salts 7 Example 3. 200 kgs. of nitronaphthalene ed by means of solvents.

are reduced in a solution of kgs. of aluminium chloride, 400 kgs. of Water and 10 kgs. of hydrochloric. acid (sp; gr. 1.16) With 200 kgs. of iron. When the reduction is complete the naphthylamine produced is extract- The remaining yel- 10W residues are freed from any remaining solvents by treatment with steam, then Washed and centrifuged. By calcination a brilliant red iron oxide is obtained.

' Example 4.-200 kgs. of nitrobenzene are reduced in LOO kgs. of a17,5% aqueous solution ride is formed.

- has nearly 203 arating the resulting l and i an iron 1 ,PIOVIDQ' the of hydrochloric acid by of iron and 6 lags. of aluminium metal; in the course of the reaction aluminium chiois obtained as a byproduct of thefreduction the same properties as in the fore going example The quantity and concentration of the hydrochloric acid used may be varied ivithin Wide limits; e. less than the amount equivalent to the aluminium metal can be used.

This application is a division of my co-- 5' ing aluminum as metallic base and an acid in amount insufiicient to dissolve the'iron, sepiron oxide sludge from the reaction mixture, and purifying the former by levigation and Washing out;

"2. In the process of reducing an aromatic nitro compound involving the treatment of e'nitro compound with a reducing agent comprising iron and an agent which is hydro lyzable in Water to produce hydrogen ions, to the production of the corresponding amine oxide sludge, the steps for im- Q pigmenting properties of the said iron oxidesludge which consists in using as the reducing agent a mixture of ironpa diarating the resulting iron lute aqueous solution of aluminum/as metallic base] and an acid in amount insufficient to dissolve the iron, sepoxide sludge from the reaction mixture, purifying the former by levigationi and Washing out, anddrying and calciningthe resulting product.

3. In the process of reducing an aromatic nitro compound involving thetreatment of the nitro compound with a reducing agent comprising iron'and an agent Which is -hysultin iron oxide slud e means of 220 kgs.

V Theiron hydroxide which a salt containing drolyzable in Water to produce hydrogen ions, to the production of the corresponding amine and an iron oxide sludge, the steps for improving the pigmenting properties of the said iron oxide sludge Which consist in using as the reducing agent a mixture of iron, a dilute aqueous solution of aluminum chloride and hydrochloric acid in amount insuflicient to dissolve the iron, separating the refrom the reaction mixture, and purifying the former by levigation and Washing out.

4. In the process of reducing an aromatic nitro compound involving the treatment'of the nitro compound With a reducing agent comprising iron and an agent which is hydrolyzable in Water to produce hydrogen ions, to the production of the corresponding amine and an'iron oxidesludge, the steps for improving the pigmenting properties of the said iron oxide sludge which consist in using as the reducing agent a mixture of iron, a dilute aqueous solution of aluminunichloride and hydrochloric acid in amount insufficient to dissolve the iron, separating the resulting iron oxide sludge fromjthe reaction mixture, purifying the former by levigation and Washing out, and dry and calcining the resulting product.

In testimony whereof I have hereunto set my hand.

' JULIUS LAUX. 

